Civil society and government authorities in Colombia are struggling to find a solution to "invasive" hippopotamuses in the wild that have been damaging crops, affecting people's lives, triggering conflicts and impacting the environment.

With an estimated headcount of 136, the herd stands as the largest colony of hippos outside Africa, where the species originated.

The hippo problem, although relatively new, had its roots in the 1980s when notorious drug lord Pablo Escobar illegally imported four of the large animals into the country, to add to his private zoo at his ranch in Puerto Triunfo, Antioquia, some 240 kilometers northwest of Bogota, Colombia's capital city.

After Escobar was killed in 1993, the hippos were left to roam freely and multiplied to over 130 in just 20 years. They are now in the Magdalena Medio region, a large valley in the Andes, settled in an estimated area of about 2,000 square kilometers, almost twice the geographic size of Hong Kong.

In March last year, Colombian authorities officially declared the hippos as an invasive species.

"It is a problem that overwhelms us and that requires the participation of many more entities, and hopefully funding with international resources," he said.

Despite the threats to the population and the impact that hippos can have on other species, their habitat and the environment, there are no final solutions in sight, although various actions have been tested, including relocation and castration.

"We have already tried various measures; we have captured them, relocated them in zoos and we have even castrated them. We have experimented with many different approaches," Echeverri said.

According to Carlos Valderrama, director at WebConserva, a non-profit foundation dedicated to the conservation and sustainable use of ecosystems in Colombia, there is already a large pool of reproductively active female hippos.

"There are at least 20 females reproductively active, which means that there could be 20 hippos born every two years," Valderrama said in interview. This is a "conservative estimate" and that there will be more reproductively active females as the population grows, he said.

Conducting surgical castration on the male population is an option, according to Valderrama, but this could cost as much as $20,000 per animal. Helicopters and cranes must be used to transport each hippo, due to its weight, which could tip the scales at four tons.

"The more time passes, the more difficult the situation becomes," Valderrama said.

Along with hippos, 22 other plant and animal species are invading Colombia, according to an official list published by the government and updated in 2022. It includes, among others, the lionfish, the American bullfrog and even rainbow and brown trout.

At the COP15 United Nations biodiversity summit held in Canada in December, the subject of invasive species was discussed. One of the goals of the Kunming-Montreal Global Biodiversity Framework is to reduce the introduction and establishment of invasive alien species by at least 50 percent by 2030.

The writer is a freelance journalist for China Daily.